Device for investigating materials

ABSTRACT

A device for examining materials, in particular trees, other kinds of wood, and concrete, with a pulse generator ( 1 ) for generating a pulse that can be introduced into the material ( 2 ), with at least one sensor ( 3 ) adapted for being associated to the material ( 2 ) for detecting the pulse, and with an electronic evaluation device ( 4 ) for discriminating the pulse from interference pulses, is designed and constructed with respect to a universal application to even large test pieces of the material ( 2 ) being examined in such a manner that an electronic evaluation device ( 4 ) is associated to each sensor ( 3 ).

BACKGROUND OF THE INVENTION

The invention relates to a device for examining materials, in particulartrees, other kinds of wood, and concrete, with a pulse generator forgenerating a pulse that can be introduced into the material, with atleast one sensor adapted for being associated to the material fordetecting the pulse, and with an electronic evaluation device fordiscriminating the pulse from interfering pulses.

Devices for examining materials of the initially described kind areknown from practice, and they exist in a large variety of types. Theyare, for example, devices, wherein the pulse time delay of shock wavesis measured. From this pulse time delay, conclusions are drawn withrespect to the quality of the material being examined. In the case ofwood, for example, utility poles, the time delay of the shock wavescorrelates in the direction of growth or grain with the modulus ofelasticity in the bending of wood, which enables an assessment of theload capacity, and the therefrom dependent categorization into qualityclasses. This influences the purchase price in the case of new poles.

In most cases, it is common to introduce into the material the shockwave or the pulse with a hammer serving as a pulse generator, either ina direct manner or via a screw or a bouncing pin. In the case of anaxial irradiation of a pole by sound waves, the pulse is typicallyintroduced at the front end. A sensor arranged at the other end of thematerial or pole detects the pulse that has been introduced into thematerial. A current pulse corresponding to this pulse is then guidedfrom the sensor to a central electronic evaluation device, where thecurrent pulse is analyzed by discriminating interfering pulses.

More specifically, an acceleration sensor in the pulse-generating hammertransmits in the instant of applying the stroke, the resultant currentpulse via a line to a central electronic unit or electronic evaluationdevice, which analyzes the pulse, and starts a clock, depending on theresult, namely a successful discrimination from, for example,interference vibrations. As soon as the sensor at the other end of thematerial or the other end of the measured length registers the arrivalof the shock wave, it will likewise transmit a corresponding currentpulse to the central electronic unit, which stops the clock, if thepulse meets the requirements with respect to intensity and length. Boththe pulse from the hammer and the pulse from the sensor must each beelectronically discriminated, i.e., be distinguished from othervibrations. This occurs each time in the central electronic evaluationdevice. For purposes of being able to distinguish between real pulsesand spurious pulses, a user may normally adjust “gain” and “offset” inthe central electronic evaluation device. From the time delay of thepulse and the distance between shock application and detector, it ispossible to determine the pulse or shock velocity. Same allows to makestatements as to the internal condition and the quality of the materialbeing examined or the test piece, not only in the case of wood, but alsoin the case of concrete and other materials.

In the known device, the electronic signals of the acceleration sensors,the pulse generator, and the detectors, are transmitted via cables to acentral electronic detection and evaluation device. This device alsoaccommodates an accurate electronic clock. The discrimination andevaluation of the pulses, which were converted into electronic currentpulses, previously introduced, and subsequently detected, thus occurs ina central location by means of corresponding electronic circuits. Inthis connection, the pulse shape is decisive for differentiating betweenreal pulses and interference pulses. Thus, the pulse shape should not bealtered or falsified on its way from the sensor through the cable to theelectronic evaluation device, for example, by electromagneticinterferences or technical cable properties. To accomplish this, thetransmission cables must be shielded and be of an extremely highquality, which leads to high prices, limited length of few meters, andrestricted handling. Cables of this kind with a corresponding shieldingreact very sensitively to low temperatures and other external effects,so that they can be used only with limitations, and are very prone tointerference. For example, for purposes of avoiding interferences, suchcables should not extend in a loop. In particular, in the case of verylong or large test pieces of the material being examined, it is notpossible to use the known device, since there exist no adequately longcables, which enable an interference-free transmission of current pulsesfrom the sensor or sensors to the central electronic evaluation device.

Consequently, the use of the known device for examining materials, inparticular with respect to large test pieces, is very restricted on thematerials being tested. A universal application of the known device istherefore not possible.

It is therefore an object of the present invention to describe a devicefor examining materials of the initially described kind, which enables auniversal application with constructionally simple means, in particularalso in the case of large test pieces of the material being examined.

SUMMARY OF THE INVENTION

The above and other objects and advantages of the present invention areachieved by a device of the type which is designed and constructed suchthat an electronic evaluation device is associated to each sensor.

According to the invention, it has first been recognized that theforegoing object is accomplished in a surprisingly simple manner alonebecause of a suitable arrangement of the electronic evaluation device.Furthermore, in accordance with the invention, a separate electronicevaluation device is associated for this purpose to each sensor. Thisassociation of respectively one electronic evaluation device to eachsensor permits avoiding great cable lengths between the sensors and theelectronic evaluation device, in particular with the use of a pluralityof sensors. In comparison therewith, it is not possible to avoid in thecase of most sensors, great cable lengths with the use of a centralelectronic evaluation device for all sensors in use, which are oftenarranged at great distances between one another.

The device of the present invention makes it now possible to perform thediscrimination of pulses quasi directly on the sensors with minimalcommunication lengths. Since an electronic evaluation device isassociated to each sensor, the spacings between the sensors are nolonger important. Therefore, it would also be possible to arrange thesensors at a great distance between one another, while yet enabling areliable discrimination of pulses.

Consequently, the device for examining materials according to theinvention realizes a device, which permits a universal application withconstructionally simple means, in particular also in the case of largetest pieces of the material being examined.

As regards the kind of pulse, two alternatives present themselves. Inthis connection, the pulse could be a mechanical and/or an electricalpulse. A mechanical pulse is, for example, a shock wave, which istriggered, for example, by means of a hammer. However, it is alsopossible to introduce electrical pulses into the material beingexamined. In this instance, it is also possible to measure the timedelay of the current pulse and/or its attenuation. The pulse may be adirect current or an alternating current pulse. In the case of thealternating current pulse, it is also possible to examine. its frequencyresponse while passing through the material.

As regards a very short and reliable communication length between thesensor and the electronic evaluation device, the latter could bearranged directly adjacent to the sensor or be integrated in the sensor.In particular, the integrated arrangement of the electronic evaluationdevice in the sensor ensures a particularly compact andevaluation-reliable configuration of the device.

As regards a particularly simple processing of the measured datagenerated by the device, the electronic evaluation device could includea device for generating an electronic signal. In this instance, theelectronic evaluation device could be designed such that the electronicsignal is generated exactly at the moment, when a real measurement pulseis detected, which is discriminated from interference pulses. In thesimplest case, the signal could be an electronic, preferably digitalstandard pulse. In this case, one has in mind in particular a TTL pulse.

It would be possible to transmit an electronic signal, which isgenerated by the electronic evaluation device, to a central unit, whichpreferably is, for example, a portable computer. In such a central unit,it would be possible to process the measured data in the form of, forexample, time delays of the shock waves from the pulse input location tothe respective sensor.

In particular with respect to a reliable transmission of the signal fromthe sensors or the electronic evaluation device to the central unit, itwould be possible to interlink the sensors and/or electronic evaluationdevice electrically. For an electrical connection, one could usestandard cables of the simplest kind, since it is not necessary tosuppress here interferences or signal distortions. What matters is onlya reliable transmission of an electronic standard signal. A costlydiscrimination in the central unit is no longer needed, since thedecisive discrimination of real pulses from interference pulses alreadyoccurs in the electronic evaluation device. It would be possible toprovide a closed-loop line or a star-shaped line. In this instance, itis necessary to accommodate the respective case of application. Thismeans that in the case of large test pieces, a closed-loop line could beadvantageous because of its shorter overall cable length as a whole.

As an alternative to a transmission via electrical lines, thetransmission could occur by means of radio waves, ultrasonic waves, orinfrared radiation. To this end, it would be possible to associate toeach sensor a transmitter-receiver unit for radio waves, ultrasonicwaves, or infrared radiation. Via such a transmitter-receiver unit, itwould be possible to transmit especially the electronic signal of theelectronic evaluation device, thereby avoiding extensive cabling.

In a concrete arrangement, one could associate a vibration detector toeach sensor. The oscillation detector is used for detecting mechanicalpulses. In a particularly simple manner, the oscillation detector couldbe a piezoelectric element.

For a reliable transmission of a mechanical and/or an electrical pulsefrom the test piece to the sensor, a transmission pin for the pulsecould be associated to each sensor. In a constructionally very simplemanner, the transmission pin could be a metal pin, preferably a steelpin. At the beginning of a measurement, such a transmission pin could beinserted into the test piece of the material being examined, whereuponthe sensor is coupled with the transmission pin. In a particularlysimple manner, the sensor could engage the transmission pin or suspendtherefrom. If the material being examined consists, for example, ofconcrete, one could do without a transmission pin.

In the device for examining materials according to the invention, onemeasures, for example, the time delay of a pulse from a pulse inputlocation to each individual sensor. In so doing, it is necessary toinitialize the sensors. To this end, a clock could be associated to eachsensor. For example, an initialization could occur in such a manner thatthe first sensor, which detects a real pulse, starts its clock and, inso doing, transmits at the same time a preferably electroniccommunication signal to the other sensors to reset their clocks to zeroand to start them likewise. This initialization principle will beespecially favorable, when the pulse is input or introduced in thedirect vicinity of the first sensor.

Once a real pulse is detected, the electronic evaluation devicetransmits, for example, an electronic signal to a central unit. In thiscase, it is advantageous to associate to each sensor an individualidentification means, so as to enable an allocation of the signalsarriving at the central unit to the respectively transmitting sensor. Tothis end, the sensors could identify themselves by a clear code.

In a further advantageous manner, it would be possible to associate toeach sensor a storage for measurement results, which enables a directreadout of the measurement results on each sensor.

Furthermore, it would be possible to associate to each sensor a displayfor the measurement results, which permits reading the measurementresults directly on the sensor.

A particularly advantageous development of the device for examiningmaterials could be provided with at least three sensors. This wouldpermit generating last but not least three-dimensional graphs of theresults with respect to the internal condition of the test piece. Themore sensors are used, the more detailed will be such a graph. In thisinstance, it is essential that the sensors can be associated to thematerial in a geometrically independent relationship from one another. Arigid arrangement of the sensors, for example, in a closed-loop form isnot necessary. For an effective evaluation of the three-dimensionalmeasurement data, it is only necessary that the geometric positions ofthe sensors be determined.

With respect to a particularly elegant and practical introduction ofpulses, the sensor or a plurality of sensors could be realized as pulsegenerators. To this end, it would be possible to associate to at leastone sensor a device for introducing pulses. Such a device could beformed, for example, by a piezoelectric element, which serves at thesame time as a vibration detector. As an alternative or in additionthereto, the device for introducing pulses could be a pin, preferably ametal pin. Such a pin could connect to the sensor via a coupling pieceof rubber. For introducing pulses, the pin could be activated by meansof a pulse generator in the form of a hammer.

As regards a reliable measurement of the pulses that are introduced bythe pulse generator, it is essential that the introduced pulses bedistinguished or discriminated from interference pulses. Interferencepulses may be generated, for example, during the examination of a treeby automobiles passing by in a neighboring street. Even people walkingby the test piece being examined may generate interference pulses abovethe ground or introduce them into the test piece. It will therefore beespecially advantageous, when the sensors or electronic evaluationdevices are able to recognize such interference pulses in eachapplication individually already before the actual measurement. To thisend, the electronic evaluation device could include means forself-calibration. In this case, the detection threshold of theelectronic evaluation device itself is adjusted to a level, which isabove the level of all previously detected interference pulses orinterference vibrations. This self-calibration step could occurcontinuously, with a self-calibration being absent during the time ofthe actual measurement. With that, it is possible to suppress asubstantial number of interference pulses right from the beginning.

As regards a simple determination of the positions of the sensorsrelative to one another, it would be possible to associate to the sensoror sensors pull-out measuring sticks. In the alternative, it would bepossible to associate to the sensor or sensors a rope with an angledisplay. The rope interconnects adjacent sensors. As a result, it wouldbe possible to determine the distance and angle from an adjacent sensor.With a known sensor size, it is possible to approximate from the sensordistances and angles of the rope connection, the geometry of the crosssection of a sample in the tested region, for example, the cross sectionof a tree.

As an alternative or in addition thereto, it would be possible toprovide an infrared or laser distance measuring instrument. Inconnection with the central unit, this would permit determining theposition of the sensors and pulse input locations and displaying them asa three-dimensional image. In this case, it is possible to compute,display, and output a three-dimensional image of the internal conditiondirectly from the determined pulse data.

For a better understanding of the teaching according to the invention,the essential aspects of the teaching according to the invention areexplained one more time in the following:

To generate within the scope of the device according to the invention,three-dimensional graphs of a condition, at least three sensors,preferably of the same type are arranged in a desired geometry aroundthe cross section or test piece being examined. In the case of standingtrees, for example four to six sensors per cross section or stem sectionwill suffice in most cases. The introduction of pulses may occur bymeans of a commercially available hammer. From the respective locationof the pulse input, which occurs in different places, a correspondingmeasured value is obtained, which results after a correspondingprocessing of the measured value, in a three-dimensional, quasitomographic cross sectional image. The pulse input may occur in anydesired places of the test piece.

In a concrete realization, each sensor comprises its own, independentelectronic control or electronic evaluation device, which includes, ifneed be, an electronic timer or a clock. After their conversion intocurrent pulses, for example, via piezoelectric crystals, the mechanicalor electrical pulses arriving from the test piece of the material beingexamined, are electronically processed and discriminated directly in thesensor. External interfering influences are thus directly suppressed inthe sensor. With that, interferences, which have so far been problematicin the transmission system—cables—are precluded. Once a pulse arrivingfrom the test piece is detected as correct, an electronic, preferablydigital standard pulse, for example, TTL pulse will be generated. Thispulse can be transmitted via simple, cost-favorable standard cables ofan almost unrestricted length, or even via radio, infrared, orultrasound, to other sensors or to a central unit. In this process, thesensors identify themselves by a clear code.

Optionally, the sensors are able to detect not only arriving pulses, butalso generate and input themselves pulses, for example, via the reversedpiezoelectric effect, inasmuch as, in principle, the same technology istherefor required.

For example, it is possible to interlink the sensors in the form of aclosed-loop line. However, the data may also be transmitted in astar-shaped configuration, or via radio, to a central unit with adisplay, storage, and output, or directly to a preferably portablecomputer. In this arrangement, the number of sensors is quasi random. Inan advantageous manner, each of these sensors identifies itself duringthe communication. It is necessary to identify the sensors only clearlyand to allocate them in their position, to the position of the pulseinput being registered during each pulse input.

In the case of trees, it may become necessary to arrange the sensors ata height of several meters. This may occur by means of telescopic rods,since the sensors may be either driven in directly or arranged ondriven-in pins.

A typical measuring sequence or process could be performed as follows.First, one determines on the test piece the correct position of thesensors. Subsequently, for example, for examining trees or wood, thesensors are mounted, screwed, flanged, preferably to pins that aredriven or screwed into the wood, so as to ensure an adequately stableconnection with the wood. Furthermore, one determines, if necessary, thethree-dimensional geometry of the test piece, which may occur in a laserand PC-assisted manner. Along with the determination of the geometry,the position of the sensors is determined. At the beginning of themeasurement, all sensors are in a so-called “standby” position.

Depending on the task being posed, the introduction or input of pulsesmay occur in one location or in a plurality of locations of the testpiece. Between the pulse input location and each sensor, this results ina measuring length with at least one individual measured value (forexample, time delay, conductivity, damping). consequently, each pulseinput results in a list of measured values for each sensor. These valuesare allocated to the respective length between the pulse input locationand sensor.

In a simple embodiment, a bouncing pin that is secured, for example,with rubber, hangs above each sensor. Via this pin, it is possible tointroduce shock waves, preferably with the use of a commerciallyavailable hammer.

In a second operation after positioning the sensors, at least one strokeis applied to the mounted pulse input pins. The advantage of thisprocedure lies in that the coordinates of the pulse input are each givenby the coordinates of the sensors that are determined in any case.

However, the pulse input may also occur in any other locations, forexample by means of a hammer and/or bouncing pin. For a directassessment of internal wood damage, this procedure will already suffice,since the examining expert is able to determine and allocate the resultsdirectly. However, if it is intended to determine and display as much aspossible a complete tomographic image, it will also be necessary todetermine the respective position of the pulse input in acorrespondingly exact manner.

The sensors are initialized either by the pulse input—via a cableconnection between the hammer and sensors—or by a first sensor, whichhas identified an arriving pulse. Initialized sensors start theirinternal clocks and determine, for example the time frequency until theyreceive the next pulse. The transmission of the electronic standardpulses via cables or radio occurs almost at light speed, and thus is byan order of magnitude faster than the transmission of shock waves. As aresult, the time delay by the electronic transmission of theinitialization has no significant effect on the measuring accuracy.

Each sensor transmits the time between initialization and pulsedetection to the other sensors and/or to the central unit, where thevalues are collected.

The results of the respective time delays are printed preferablydirectly on paper or shown on any portable, for example, watertightdisplay.

The evaluation may be assisted by a computer, in that the display isconnected to such a computer, or that direct use is made of a portablepersonal computer. The point of the shock wave input and sensorpositions are entered either manually or graphically, or theyautomatically result from the fact that the sensor, next to which astroke was applied, signals a zero time delay.

From the time delays of the respective connection segments between pulseinput and sensor, quasi tomographic cross sectional images of thecondition of the test piece result automatically. The number ofconnection segments and thus of the results is obtained as a function ofthe number n of the sensors, as follows:

If the pulse input does not directly occur on one of the sensors, n timedelay results will be obtained per pulse, whereas n−1 results will beobtained, if the pulse is input directly on a sensor.

If the pulse is input on each sensor, n(n−1) results will be obtained.In the case of only six sensors, and thus six shock input points on onetree, thirty measuring segments are obtained with correspondinginformation about the delay time, which results in a quasi tomographiccross sectional image. Since only few seconds are needed per pulseinput, it is possible to determine in this way in a very short time acomprehensive information about the internal condition.

For example, when two sensor rings are arranged at different heights ona standing tree, for example, at foot level and head level, one willautomatically obtain comprehensive data about the condition of theentire volume between these two rings. From two rings with six sensorseach, 12 pulse inputs—one each next to the sensor—result in a total of132 connection segments with corresponding time delay information. Fromthis, it is possible to compose a relatively accurate image of thecondition of the wood.

The device of the present invention is not limited to a certainarrangement of the sensors—for example, around a cross section. Rather,it is possible to position the sensors freely. Likewise, since thenumber of sensors is not limited, it is thus also possible to determinethe accuracy of the three-dimensional coverage of the test piece, sincethe accuracy is defined by the number and position of the sensors aswell as the number of pulse inputs. An EDP-assisted coverage of theposition of the sensors and pulse input, as well as a correspondinglyautomated evaluation enable an easy processing of the number ofresulting values, which rapidly increases with the number of sensors. Inthis process it is necessary to determine or input only the geometry ofthe sample and the arrangement of the sensors.

The geometry or surface topology of the test piece and the position ofthe sensors are the basis of further evaluations. The accuracy of theircoverage defines the accuracy and expressiveness of the results. Thiscoverage may be sketchy or occur by means of commercially availabledistance measuring instruments. Likewise useful are laser distancemeasuring devices and position recording devices.

The device of the invention permits measuring the chronological andspatial intensity distribution of the pulses. In this connection, it ispossible to input not only individual pulses and record their arrival,but also pulse sequences of identical or fluctuating intensity andfrequency.

The electronic evaluation device comprises means for discriminating thepulse from interference pulses. In this connection, it would here bepossible to integrate a corresponding software.

In a particularly advantageous manner, the device is made waterproof foroutdoor use, thereby ensuring a long and troublefree operation of thedevice.

It would be possible to place the sensor not only on a pin, but also ona star-shaped pin combination, which includes pin tips pointing indifferent directions. When the arriving pulses are separately detected,each by the individual tip, it will be possible to determine resultsover the spatial direction of the pulses, which is very interesting inthe case of trees, since there are different radial and tangentialpropagation responses.

The bouncing pin, which can be actuated either by a hammer or a sensor,may be oriented in a different direction. This permits taking intoaccount a different propagation response in the material.

In the device of the present invention, a plurality of sensors enablequasi tomographic determinations of the internal condition with only fewmeasurements. In this instance, identically adjusted sensors of only onekind are needed, which reduces the costs of manufacturing. The sensorsevaluate pulses from the material being examined directly,independently, and thus “in situ”, which reduces sources of interferenceand expense. For example, the shock input may occur by means of acommercially available hammer, which is very flexible andcost-favorable. The sensor connection requires only simple, commerciallyavailable, and cost-favorable connection cables, or it may occur viaradio or other methods of remote transmission, since only electronicstandard pulses are transmitted, which are insensitive to externalinterferences.

Based on the technical characteristics of the system, it is possible toposition on the test piece, without limitation, any desired number ofsensors. As a result of using a sensor shielding, standard cables, andtransmitted pulses, the device is extremely insensitive toelectromagnetic interference radiations, incorrect handling, mechanicalloads, and other disturbances.

Quasi tomographic cross sectional images result in an automatic and avery simple way.

Volume-relevant results are obtained with the use of as few as threesensors. A plurality of sensors permits in a simple manner athree-dimensional coverage of the condition of almost any desired kind.A measurement can occur very rapidly by first inserting the pins, thenmounting the sensors, and subsequently generating pulses by a shock orin any other fashion. Finally, the measurement results are noted orrecorded. Only few minutes are needed for the therefor required twoloops around the tree.

There exist various possibilities of improving and further developingthe teaching of the present invention in an advantageous manner. To thisend, reference may be made to the following description of an embodimentof the device according to the invention with reference to the drawing.In conjunction with the description of the preferred embodiment of thedevice according to the invention with reference to the drawings, alsogenerally preferred improvements and further developments of theteaching are described.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic view of an embodiment of the device according tothe invention for examining materials in a state arranged on a tree; and

FIG. 2 is a schematic top view of a sensor of the embodiment of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a schematic view of the embodiment of the device according tothe invention for examining materials. The device comprises a pulsegenerator 1 for generating a pulse that can be introduced into amaterial 2. A tree is used as the material 2 being examined.Furthermore, the device includes six sensors 3 associated to thematerial 2 for detecting the pulse with six electronic evaluationdevices 4 for discriminating the pulse from interference pulses. Asregards a universal application of the device to even large test pieces,a separate electronic evaluation device 4 is associated to each sensor3.

The electronic evaluation device 4 performs the discrimination of realintroduced pulses from interference pulses. No long communication pathsare needed between the sensor 3 or a vibration detector and theelectronic evaluation device 4. In the illustrated embodiment, theelectronic evaluation device 4 is integrated in the sensor 3. Thesensors 3 are connected to the material 2 by means of a transmission pin5. In this connection, the sensors 3 engage the transmission pin 5 orsuspend therefrom. By way of example, a device for introducing pulses isassociated to one of the sensors 3 in the form of a pin 6. The pulsesare introduced by a stroke with the hammer on pin 6.

The sensors 3 are interlinked via connection cables 7. Furthermore, aconnection is provided between the sensors 3 and a central unit 8. Thecentral unit 8 receives electronic signals, which are generated by theelectronic evaluation devices 4 of the respective sensors 3, when a realpulse is detected. In this process, an individual code is determined foreach sensor 3, so that the central unit 8 is able to allocate thearrival location of the detected pulse.

FIG. 2 is a schematic top view of a sensor 3 of the embodiment of FIG.1. The sensor 3 includes an integrated electronic evaluation device 4.The pin 5 serving to connect to the material is coupled with the sensor3 via a coupling piece 9. In direct connection with the coupling piece9, a vibration detector 10 is provided, which is formed by apiezoelectric element. The electronic evaluation device 4 and thevibration detector 10 are coupled via an electric connection 11.

Both the transmission pin 5 and the coupling piece 9 may be made of aconductive material, preferably metal. This ensures not only atransmission of vibrations from the material 2 to the vibration detector10, but also a transmission of electrical pulses to the vibrationdetector 10 and, thus, via the electrical connection 11, to theelectronic evaluation device 4. With that, it is possible to detect withthe sensor 3 not only mechanical, but also electrical pulses.

The transmission of an electronic signal, which is generated by aspecial device associated to the electronic evaluation device 4, or ofother signals from the sensor 3 may occur as an alternative to thetransmission via cables 7, via a transmitter-receiver unit 12 for radiowaves, ultrasonic waves, or infrared radiation. The transmitter-receiverunit also permits an initialization of the sensors 3 at the beginning ofa measurement. In this case, the connection cables 7 may be omitted. Thetransmitter-receiver unit 12 may be used for transmitting all kinds ofsignals, measurement results, or the like.

The electronic evaluation device is used as an independent unit with acentral processing unit.

As regards further advantageous developments of the device according tothe invention for examining materials, the general part of thedescription as well as the attached claims are herewith incorporated byreference for purposes of avoiding repetitions.

Finally, it should be expressly pointed out that the above-describedembodiment of the device according to the invention merely serves todescribe in greater detail the claimed teaching, but without limiting itto this embodiment.

What is claimed is:
 1. A device for examining materials comprising a pulse generator for generating a pulse that can be introduced into the material, at least one sensor configured for being positioned with respect to the material so as to detect the pulse, and an electronic evaluation device for discriminating the pulse from interfering pulses, with the electronic evaluation device and the at least one sensor being integrated in a unitary one-piece structure, whereby the pulse evaluation may be effected adjacent the sensor with minimal communication paths and minimal electromagnetic interference.
 2. The device of claim 1 wherein the pulse is a mechanical and/or electrical pulse.
 3. The device of claim 1 wherein the electronic evaluation device includes means for generating an electrical signal.
 4. The device of claim 3 wherein the electrical signal is connected for transmission to a central unit.
 5. The device of claim 4 wherein the central unit comprises a personal computer.
 6. The device of claim 1, wherein said device comprises a plurality of said sensors, and wherein an electronic evaluation device is integrated with each sensor as part of a unitary structure.
 7. The device of claim 6 wherein said sensors are electrically interconnected.
 8. The device of claim 6 wherein each of the sensors is operatively connected to a central unit.
 9. The device of claim 6 wherein each of the sensors is operatively connected to a central unit via a transmitter-receiver unit associated with each sensor.
 10. The device of claim 6 wherein each of the sensors has a vibration damper associated therewith.
 11. The device of claim 10 wherein each vibration damper is a piezoelectric element.
 12. The device of claim 6 wherein a transmission pin for detecting the pulse is associated with each sensor.
 13. The device of claim 6 wherein a clock is associated with each sensor.
 14. The device of claim 6 wherein an identification symbol is associated with each sensor.
 15. The device of claim 6 wherein a storage for measurement results is associated with each sensor.
 16. The device of claim 6 wherein a display for measurement results is associated with each sensor.
 17. The device of claim 6 wherein said pulse generator comprises means for introducing electrical pulses into the material being examined.
 18. The device of claim 6 wherein said pulse generator is mounted to at least one of said unitary structures for introducing pulses to the material being examined.
 19. The device of claim 18 wherein said pulse generator includes a pin.
 20. The device of claim 6 wherein said pulse generator comprises a hammer.
 21. The device of claim 6 wherein each electronic evaluation device includes means for self calibration.
 22. The device of claim 6 wherein each sensor is connected to a pull out measurement stick.
 23. The device of claim 6 wherein each sensor is connected to a rope with an angle display.
 24. The device of claim 6 further comprising an infrared or laser distance measuring instrument for measuring the position of each sensor. 